Clarification



Aug. 18, 1953 A. M. KIVARI ETAL CLARIFICATION 3 Sheets-Sheet 1 FiledApril 13, 1951 kings lll Aug. 18, 1953 A. M. KlVARl ET AL CLARIFICATIONFiled April 13, 1951 5 Sheets-Sheet 2 INVENTORS. ARTHUR M. K/I/AR/ EARLM. KELLY "HAM/"annual,

ATTORNEY be mixed with previously formed flocs.

Patented Aug. 18,1953

I UNITED STATES PATENT ()FFlsC E CLARIFICATION Arthur M. Kivari, LosAngelcs, andEarl M. Kelly, Burlingame, Calif., assignorstoProce'ss Enginecrs Incorporated, San Francisco, .Galif., .a corporation of CaliforniaApplication April 13, 1951, Serial No. 2205776 11 Claims.

This invention relates to clarification and --more particularly toclarification oisewage. It

provides improved clarifying apparatus particularly adapted for sewagetreatment but use- -ful in other processes involving the separationofsolids from liquids by settlement.

In U. S. Patent 2,506,927, granted May 9,1950, one of us describessewage treatment with aeration, coagulation and sedimentation in asingle circular tank. lhe infiuent, say raw sewage, entore the tankthrough a central column and discharges into an inner circularcompartment separated from the outer or rim portion of the tank by anupright annular bafile extending above the liquid level in the tank butopenat the'bottom. In the inner circular compartment the influent isaerated :and circulated and may Liquid and unsettled solids pass intothe outer annular compartment for "upfiow sedimentation. Settled solidsdeposited in the bottom of either the outer compartment or the innercompartment are raked-down the gently sloping inverted conical surfaceof the tank bottom to a central sludge outlet and then discharged.Clarified effiuent overflows a peripheral weir at the upper rim of thetank.

The foregoing apparatus has -met with outstanding commercial success. Ithas been particularly successful in sewage treatment, where economicalclarification is achieved by concentrating solids in an aerobicenvironment which is conducive tothe flocculation of colloidal andgelatinous suspended matter. However, in some instances the sludgeproduced is not as dense as is desired.

As a result of our investigations we have developed an improvedapparatus in which the benefits heretofore secured by the apparatusdescribed and claimed in U. S. Patent 2,506,927 are still obtained andin which it is possible to producedenser sludge. This is accomplished byraking settled sludge from both the inner and outer compartments to oneor more non-central discharges which may be located anywhere in thebottom of the outer compartment or in the bottom just within'the inneror agitation compartment, i. e. immediately inside and below the battlewhich separates the inner or aeration and agitation compartment from theouter or sedimenta- 'tion compartment.

In the preferred for-m of the apparatus, means isprovided for returningsludge from a point in or near the sludgesu'mp or outlet intotheagitation compartment for further mixing and circu- Ja-tion withinfiuent. In this fashion, fine 'floc already formed is used to seed theincoming sewage or other-influent. This brings --about better and fasterflocculation of colloidal and gelatinous -ma-ter ial in the feed and atthe same time increases the particle size-of the initial floc so as tofurther increase settlement rate and sludge density.

'These and other aspects ofour invention will be understood morethoroughly in the light of the following detailed description taken inconjunction with the accompanying drawings, in which:

Fig. 1 is a vertical elevation, partly in section, through one form ofthe apparatus of our invention, in which settled solids are moved to theouter rim of the apparatus Fig. 2 is a fragmentary plan view of theapparatus of Fig. 1;

Fig. 3 is a vertical elevation, partly in section, through a modifiedform of the apparatus of Figs. 1 and 2;

"Fig. 4 is a fragmentary vertical elevatiom-partly in section, throughstill another modification of the apparatus of Figs. 1 and 2;

Fig. 5 is a verticalfragmentaryelevation, partly in section, throughanother term of the apparatus; "and Fig. 6 is a fragmentary verticalelevation Jillustra-tin'g a modification of the apparatus of Fig. '5.

The apparatus of Fig. 1 comprises an upright cylindrical and relativelyshallow tank 10,, .havingra vconcrete outside .wall N. This wall ca riesan annular launder l2 at itsupper periphery i to which clarifiedefiiuent overflows over a circular weir 12A. The concrete bottom l'3 ofthe tank is inthe form of a flat cone which slopes gently outward to aperipheral sludge pocket 114 adjacent the lower portion of the wall,

sludge being withdrawn from this pocket by a plurality of outlets [5,1'6. Material to be treated, say raw sewage from which tramp iron,coarse wood and some grit has been removed, is introduced into theapparatus from the bottom through a central riser H.Theriser-opens-i-nto a central column l-8 which *is rotatable around theupright axis of "the tank and 'is supported in 'a submerged bearing l9at the bottom of the column. The 'infiuentescapes from the columnthrough a plurality of outlet ports "20 near its 'top 'nearthe liquidlevelmaintained in the tank bythe weir and enters a-centralor aerationcompartment 2 This is defined by an annular b'afile :22 that extends:above -the liquid level in the tank and drops vertically to a levelnear the bottom where it terminates in an inverted frusto conicalextension 23. This baflie and its extension is supported by a radialcage structure 24 that is fastened to the central column and rotateswith it. The cage also provides support for radial rake arms 25, 26which extend under the baflie from the central column to the lowerperiphery of the tank. These arms carry rakes 21 which move settledsolids in a spiral path from the center column to the peripheral sludgedis: charge pocket. The outer ends of the arms carry upright scrapers28, 29 which drop into the Sludge pocket and rotate slowly in thisannular trough, thereby moving the sludge toward the several dischargepipes and preventing it from accumulating.

If desired, the annular baffle may be supported by radial trussesdisposed in the sedimentation compartment and fastened to the outsideWall, for example, after the fashion disclosed in our co-pendingapplication Seria1 No. 96,184, filed May 31, 1949, now Patent No.2,568,452.

If scum tends to form on the pool in the sedimentation compartment,conventional skimming devices may be employed.

A conventional superstructure 30 extends across the tank at the top andis supported on the outside wall of the launder l2. It is provided withthe usual walkway 3| and handrail 32. The central column has ahorizontal ring gear 33 mounted on its upper end. This gear rests uponan annular bearing 34 fastened to the superstructure and is driven by asecond gear 35 that in turn is rotated by a motor 38 mounted on thesuperstructure.

The contents of the agitation compartment is aerated by a grou ofhorizontal radial air dispersers 31, 38 that are fed by an air manifoldpipe 39 which in turn receives air from feed pipes These pipes areconnected to a vertical air supply line 42 on the axis of the column.This line is connected through a rotatable joint 43 with a blower 44mounted on the superstructure.

Compressed air is blown into the aeration compartment through the radialair diffusers and thi induces a circulation of the contents as indicatedby the arrows. The inverted frusto-conical section at the bottom of thebaffle helps to divert the circulating stream inwardly toward the.center column.

In operation, the inflowing sewage rises in the center column and passesout through the radial outlets near the top of the pool of materialundergoing treatment in the tank. Flocculation and settlement of thesolids contained in the sewage are facilitated by the aeration andcirculation action which has just been described and which takes placein the inner 0r agitation compartment. In addition, the air maintains anaerobic condition in the sewage and helps to satisfy its biologicaloxygen demand. Some solids tend to settle at the bottom of the aerationcompartment, from whence they are moved by the rakes toward the annulardischarge pocket or trough 14 at the periphery of the apparatus.However, the bulk of the solids remains suspended in the liquid and flowout into the outer annular sedimentation zone which is relativelyquiescent; The bulk of the settlement occurs here and solids, as theysettle, join those from the bottom of the aeration compartment and areraked outwardly into the discharge pocket and removed as sludge throughthe pipes l5, l6.

4 Clarified liquid overflows at the top of the apparatus into theperipheral launder I2.

The principal advantage of the apparatus of Figs. 1 and 2 resides in thefact that a settled sludge of a higher density can be removed from theapparatus.

The denser sludge represents acleaner separation of solids and liquidand sludge of higher density is easier to handle in subsequent treatmentsteps. Moreover, the return of a denser but still finely divided sludgeto the coagulation going on in the aeration zone facilitates suchcoagulation and increases the throughput of the apparatus.

The apparatus of Fig. 3 is, in general, similar to that of Figs. 1 and2, like parts being indicated by like reference characters. Thestructure of Fig. 3 differs as follows:

The central column through which the influent is introduced is anannular concrete pier 50 which supports a drive mechanism 5! of the typedescribed and claimed in co-pending application Serial No. 222,457,filed April 23, 1951, by Samuel I. Bousman. The pier has an enlargedfrustoconical base 52 which tends to divert the circulating stream inthe aeration compartment upwardly along the pier wall as indicated bythe arrows.

Secondly, the apparatus of Fig. 3 is provided with valves 54, 55 on theoutlet lines l5, l6 to control the rate of withdrawal of sludge to apump, not shown.

The apparatus illustrated in Fig. 4 is of the traction type, rotation ofthe rake mechanism being accomplished by a motor 60 mounted on the outerend of a radial beam BI and driving a traction wheel 62 which rides on aperipheral track 63. The tank is provided with the conventionalperipheral launder 64 at its upper rim and with a vertical circular sidewall 65 which supports the launder. The bottom of the tank slopes gentlyin two directions. Thus the inner portion 68 below the agitation zone 66defined by the annular baflie 61 is conical from the inside toward oneor more discharge pockets 69 extending around the apparatus almostunderneath the bafiie. The outer portion H3 of the bottom is an invertedfrusto-conical section sloping gently in the opposite direction from theouter Wall toward the discharge.

In the apparatus of Fig. 4 the baflle which defines the inner oraeration zone is supported from the bottom on piers 12, there beingsubstantial gaps between pier to permit passage of material underneaththe bafile.

Feed for the apparatus of Fig. 4 enters'the central feed well '33 andrises upward in a central column 14 from which it escapes through ports75 and thence through ports 16 into the agitation or aeration zone. Theinner end of the beam 6.l is rotatably supported by a bearing structure11 resting on the top of the column. An inner cage 18 is fastenedrigidly to the beam and carries rake" arms 19, 80. These in turn carryrakes 8| which are slanted so as to cause solids settling in theagitation compartment to travel outward into the discharge pocket 69.Solids settling into the discharge pits are withdrawn through radialpipes 82 extending outwardly below the apparatus.

Each rake arm carries a radial pipe 83, 84 which ends in a downwardlyprojecting elbow 85. These elbows terminate just above the dischargepocket. The pipes are connected with an annular circulating column 86which extends up- .wardly around the influent column. ;A vertical therotating upper beam Si by trusses .93.

bottom I04.

coaxial air lines! provided withbranchesilB, 89 rises upwardly to.connect with a circular air dis- Derser 98 inside the annular circulatincolumn. This air disperser causes the annular return or circulatingcolumn to act as an airlift and to suck partially settled sludge frompoints adjacent the end of the elbow upwardly in the column to be mixedwith the fresh infiuent and discharged into the agitation zone withinthe baffle.

.Here the contents of the agitation zone are fur .ther aerated bydispersers as in the case of the apparatus of Figs. 1 and 2.

That portion of the tank between it outside wall and the baflieconstitutes a sedimentation zone 9! in which settlement takes placeunder relatively quiescent conditions. It :is provided with radial rakearms 92 rigidly suspended from The rake arm is provided with rakes 94 soslanted that they tend to move settled solid inwardly toward thedischarge pockets 69.

In the operation of the apparatus of Fig. 4, raw sewage to be treatedisintroduced into the center of the apparatus where it meets returnedpartially settled sludge rising in the air lift column 86. The mixtureis discharged into the agitation zone where circulation is caused as inthe previous case, by the air diifusers. Coagulation and flocculation ofsolids results and such solids as settle are raked toward the dischargepocket at the periphery of the agitation zone. Liquid and solids whichdo not settle to the bottom of the agitation zone .fiow underneath thebaffle into the outer or sedimentation zone and are there settled underquiescent conditions, clarified efiluent overflowing into the peripherallaunder. Solids settling in the outer sedimentation zone are also rakedto the discharge pocket. Any solids not recirculated through the returnpipes carried by the inner rake arms are withdrawn from the apparatusand discharged.

The form of apparatus illustrated in Fig. 4 is particularly desirable inthe larger sizes. As

shown, it is of the traction type, and tosimplify construction itsbafile is supported from the bottom rather than with the rake arms. Theuse of a plurality of sludge pockets insteadof a single annular oneeliminates the scrapers employedin the latter and further reduces thepower requirement of the equipment.

The apparatus of Fig. is similar .to that of Fig. 4, with the followingexceptions:

It is not of the traction type. vIts bafile I00, which defines the inneror agitationzone, is carried by the rake arms ml, the entire internalstructure being rotated by conventional means,

not shown.

The sludge pocket I02 is annular and extends completely around thebottom just outside the bafile.

The rakes I03 on the rake arm below the agitation zone tend to movesettled sludge outwardly to the sludge pocket along a substantiallylevel The rakes I05 below the sedimentation compartment are slanted inthe opposite direction'so as to move settled sludge down the gentlysloping floor section I06 into the sludge pocket. The rake arms areprovided with scrapers l0! which extend into the annular sludge pocketand tend to move the sludge toward the discharge pipes H18 and preventthe sludge from accumulating.

Adjacent the scrapers are the inlet ends [09 of sludge return pipesllil. These connect to an annular airlift column lll as described forFig.

4. The top of this annular airlift column flares outwardly with aninverted .frusto-conical diverter H2 disposed above it so that therising suspension of solids in liquid tends to be thrown out radiallyall aroundthe column. Air for'the lift is supplied to a circumferentialair ring H3 by an air pipe I M which is mounted on the'vertical axis ofthe apparatus and drops down from above.

In the .operation'of the apparatus of.Fig.;5, raw sewage to be treatedenters the center of the apparatus, rises through the center columnlidand out through ports H6 into theannular airlift column wheretheincoming sewagemixes with returned partially settled sludge. Themixture is ejected intothe aeration zone where it is aerated and causedto circulate. as indicated by, the arrows, the circulation beingaccomplished by air dispensers H! as described in the case-of Figs. 1and. 2. Such solids as settle to the bottom of the agitation zone areraked outwardly into the sludge discharge as previously described. Thebulk of the solids do not settle in the agitation zone but passunderneath the baffle to the sedimentation zone I8 where settlementoccurs under'quiescent conditions, the resulting sludge being, rakedbackward toward the annular sludge pocket. The return pipe I I0withdraws partially settled sludge which may'comefrom either theaeration zone or the settling zone backward through the central columnfor recirculation in the aeration zone to accomplish the'increasedsettlement and improved flocculation described previously.

Fig. 6 illustrates a modification-of the apparatus in Fig. 5, whereinthe annular sludgepocket, instead of being disposed immediately outsidethe battle which separates aeration and sedimentation zones, is disposeda substantial distance outside the barrier and well into thesedimentation zone. This is desirable in some instances, where it isdesired to return a somewhat larger proportion of more'completelysettled solids to the aeration-recirculation operation in the agitationzone.

As indicated at the outset, the apparatus of the invention in theseveral .forms illustrated,

brings about excellent clarification and aeration of sewage and othersuspensions of solids in liquids and results in the production of athicker sludge or overflow than has heretofore been ob- .tained.

. The apparatus of theinvention accomplishes a more thoroughprecipitation and settlement of .finely divided solids than doestheconventional clarifier, probably as a result of the aeration and therecirculation of nuclei which aidfiocculation and coagulation. Inconsequence, thereis a tendency to form a large mass-of relatively thinsludge formed of very .fine particles. Such a sludge takes a long timeto settle in the region just above the bottom. Hence, inorder to form adense .or thick sludge, it is desirable toprovide a relatively largesludge pocket in which the sludge has a longer retentionperiodand agreater opportunity to thicken by settlement. Itis .for this reason thatthe annular sludge pocket, with its comparatively large volume,ispreferred over a single pocket or .series of pockets scattered aroundthe bottom.

We claim:

1..In apparatus for separating solids from sewage by settlement andincluding a tank having an inner compartment and an outer sedimentationcompartment disposed around it, the

two' compartments communicating with" each other justabove the tankbottom but separated from each other at higher levels by an annularimperforate baflle, means for introducing the sewage into the innercompartment, and means for withdrawing clarified sewage from an upperportion of the outer compartment, the combination which comprises asludge pocket located below the bottom of the tank and at a level lowerthan that of the bottom of the bafile within the region which beginsunderneath the baflle and which extends to the periphery of the tankbottom, means disposed in the inner compartment for aerating thecontents thereof to cause an up-and-down circulation of liquid andsolids in the sewage between an intermediate and an upper portion of thecompartment to bring about flocculation of finely divided solids in thesewage, raking means extending along the bottom substantially to thepocket for raking settled solids along the tank bottom into the pocketfrom the tank bottom underlying both compartments, and means forwithdrawing solids from the pocket.

2. In apparatus for separating solids from sewage by settlement andincluding a tank having an inner compartment with an outer sedimentationcompartment disposed around it, the two compartments communicating witheach other just above the tank bottom but separated from each other athigher levels by an annular imperforate baflle, means for introducingthe sewage into the inner compartment, and means for withdrawingclarified sewage liquid from an upper portion of the outer compartment,the

combination which comprises an annular sludge channel extending aroundthe tank and located in the bottom of the tank at a level below that ofthe bottom of the bafile and within the region which begins underneaththe bafile and which reaches to the periphery of the tank bottom, meansdisposed in the inner compartment for aerating the contents thereof andcausing the contents to circulate between an intermediate and an upperlevel therein with resultant flocculation of finely divided solids,raking means along the bottom extending substantially to the channel forraking settled solids into the channel immediately over the tank bottomunderlying both compartments, and a conduit for withdrawing solids fromthe channel.

3. Apparatus according to claim 2 provided with a scraper disposed inthe channel, and means for rotating the scraper around the channel tocarry the solids to the conduit.

4. In apparatus for separating solids from sewage by settlement andincluding a tank having an inner compartment with an outer sedimentationcompartment disposed around it, the two compartments communicating witheach other just above the tank bottom but separated from each other athigher levels by an'annular imperforate bafile, means for introducingthe sewage into the inner compartment, and means for withdrawingclarified sewage liquid from an upper portion of the outer compartment,the combination which comprises a sludge sump located in the bottom ofthe tank in the region which begins underneath the bafiie and whichextends to the periphery of the tank bottom, means disposed in the innercompartment at an intermediate level for aerating the contents thereofand causing circulation of the aerated contents up and down between theintermediate level and an upper level in the inner compartment withresultant flocculation of finely divided solids, rak- 8 m meansextending along th bottom substantially to the sump for raking settledsolids into the pocket from and over the tank bottom underlying bothcompartments, means for withdrawing solids from the sump, and means forwithdrawing settled solids from the region of the sump and returningthem to th inner compartment.

5. Apparatus according to claim 4 in which the means for withdrawingsettled solids from the region of the sump and returning them to theinner compartment comprises an airlift.

6. Apparatus according to claim 4 in which the means for withdrawingsettled solids from the region of the sump and returning them to theinner compartment comprises an airlift disposed in the central portionof the tank and a rotatable pipe extending from the airlift to saidregion.

'7. In apparatus for separating solids from sewage by settlement andincluding a tank having an inner compartment with an outer sedimentationcompartment disposed around it, the two compartments communicating witheach other just above the tank bottom but separated from each other athigher levels by an imperforat annular bafiie, means for introducing thesewage into the inner compartment, and means for Withdrawing clarifiedsewage liquid from an upper portion of the outer compartment, thecombination which comprises a sludge sump located below the bottom ofthe tank in the region which begins underneath the baffle and whichextends to the periphery of the tank bottom, means disposed in the innercompartment for aerating the contents thereof and causing the aeratedcontents to circulate up and down in the inner compartment withresultant flocculation of solids, raking means extending along the tankbottom substantially to the sump and rotatable about the upright axis ofthe tank for raking settled solids across the tank bottom into the sumpfrom the tank bottom underlying both compartments, and means forwithdrawing the settled solids from the sump.

8. Apparatus according to claim '7 in which the raking means comprises aradial arm, and means is provided for returning the settled solids fromthe neighborhood of the sump to the inner compartment comprising a pipesupported by the arm and means for forcing the solids through the pipes.

9. Apparatus according to claim 7 in which the raking means comprises anarm extending outwardly from the center of the tank and carrying aplurality of rake members, and with the bottom of the tank slopingdownwardly and outward toward the region of the sump.

10. In apparatus for separating solids from sewage by settlement andincluding a tank having an inner compartment with an outer sedimentationcompartment disposed around it, the two compartments communicating witheach other just above the tank bottom but separated from each other athigher levels by an imperj forate annular baflle, means for introducingthe sewage into th inner compartment, and means for withdrawingclarified sewage liquid from an upper portion of the outer compartment,the combination which comprises a sludge pocket located below the bottomof the tank and the bottom of the bafile in the region beginningunderneath the baffle and extending to the periphery of the tank bottom,means for agitating the contents of the inner compartment with air andfor causing the aerated contents to circulate up and down in the innercompartment with resultant flocculation of solids, raking meansextending along the bottom substantially to the pocket for rakingsettled solids directly into the pocket across the tank bottomunderlying both compartments, and means for withdrawing solids from thepocket.

11. In apparatus for separating solids from sewage by settlement andincluding a tank having an inner compartment surrounded by an outerannular sedimentation compartment with the two compartmentscommunicating with each other only at'a level slightly above the tankbottom, means for introducing the sewage into the inner compartment andmeans for withdrawing clarified sewage effluent from the upper rimportion of the outer compartment, the combination which comprises asludge pocket in the bottom of the outer compartment, means extendingalong the bottom substantially to the pocket for 10 raking settledsolids into the pocket across the bottoms of both compartments, meansfor aerating the contents of the inner compartment and for causing theaerated contentsto circulate up and down in the inner compartment withresultant flocculation of solids, and means for withdrawing the settledsolids from the pocket.

ARTHUR M. KIVARI. EARL M. KELLY.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,291,772 Talbot et al Aug. 4, 1942 2,568,452 Kelly et a1.Sept. 18, 1951 FOREIGN PATENTS Number Country Date 333,974 Great BritainAug. 28, 1930

1. IN APPARATUS FOR SEPARATING SOLIDS FROM SEWAGE BY SETTLEMENT ANDINCLUDING AND AN OUTER SEDIING AN INNER COMPARTMENT AND AN OUTERSEDIMENTATION COMPARTMENT DISPOSED AROUND IT, THE TWO COMPARTMENTSCOMMUNICATING WITH EACH OTHER JUST ABOVE THE TANK BOTTOM BUT SEPARATEDFROM EACH OTHER AT HIGHER LEVELS BY AN ANNULAR IMPERFORATE BAFFLE, MEANSFOR INTRODUCING THE SEWAGE INTO THE INNER COMPARTMENT, AND MEANS FORWITHDRAWING CLARIFIED SEWAGE FROM AN UPPER PORTION OF THE OUTERCOMPARTMENT, THE COMBINATION WHICH COMPRISES A SLUDGE POCKET LOCATEDBELOW THE BOTTOM OF THE TANK AND AT A LEVEL LOWER THAN THAT OF THEBOTTOM OF THE BAFFLE WITHIN THE REGION WHICH BEGINS UNDERNEATH THEBAFFLE AND